The presently described technology relates generally to alkyl lactyllactate and alkoxylated alkyl lactyllactate compounds that can be used as solvents in a variety of applications. In particular, the alkyl lactyllactate and alkoxylated alkyl lactyllactate compounds, and compositions comprising or incorporating such compounds, are suitable for use in oil field applications, gypsum foamers, paints and coatings, adhesives, or other applications requiring the use of a solvent to, for example, improve cold tolerance performance (e.g., applications requiring cold weather performance without inclusion of additional volatile components) or effect the coalescent of a polymer film. The alkyl lactyllactate compounds of the present technology are also suitable for use in compositions for degreasing and stain removal.
Solvents are used in a wide variety of industrial applications. Success of the operation in which the solvent is used is highly dependent upon proper solvent selection. Thus, the characteristics of a solvent are an important consideration in determining whether a solvent will be suitable for a particular application. For many industrial processes, it is desirable that the solvent be non-hazardous, have low volatile organic compound (VOC) emissions, and have a high flash point. Other desirable characteristics, depending upon the end use, include the ability to control solvent polarity to enable the solvent to dissolve in oils and/or water, pour point depression, and support high loading of solids.
U.S. Pat. Nos. 2,350,388 and 2,371,281 (Claborn) (the “Claborn patents”) generally describe that an alkyl lactyllactate can allegedly be produced by heating a mixture of a dry lactide and a desired anhydrous alcohol at a temperature of about from 70° to 90° C. for a period of about from 6 to 8 hours in the presence of an acid catalyst under anhydrous conditions. The Claborn patents also generally describe that alkyl lactyllactates have properties asserted to be desirable for solvents and plasticizers and also have properties that are said to be desirable for use in the preparation of other plasticizers.
The process to prepare alkyl lactyllactates as described in the Claborn patents, however, requires a solvent in the reaction mixture, which is either an excess amount of the alcohol or an inert organic liquid, such as benzene. The Claborn patents also require a reaction temperature of above 70° C. It is desirable, however, to eliminate the use of solvents in the reaction process and/or to have a process that can run at a lower reaction temperature. Further, the Claborn patents do not appreciate the effect of chirality of the alkyl lactyllactate on its properties and do not teach how to make alkyl lactyllactate with different chiralities. Nor do the Claborn patents appreciate the effects of the choice of alcohol (or another hydroxyl containing compound), and in particular the effects of alkoxylation, on the product yield, purity of the product, and properties of the product. It is desirable, however, to have a process that can produce a better yield of a higher purity alkyl lactyllactate product without distillation or other purification. It is also desirable to make and use an alkyl lactyllactate with a selected chirality to achieve or improve certain desired product properties.
U.S. Pat. No. 3,144,341 (Thompson) (the “Thompson patent”) discloses stearyl lactyllactate and cetyl lactyllactate produced by reacting stearyl alcohol or cetyl alcohol with lactic acid. The stearyl lactyllactate and cetyl lactyllactate so produced are generally described as emulsifying agents particularly suitable as shortening addition agents in cake mixes and the like. The Thompson patent states that the reaction product is a mixture of stearyl lactyllactate and stearyl lactate, which are referred to as stearyl lactoyl lactate and stearyl lactate, respectively. Col. 3, lines 29-31. The Thompson patent further states that stearyl lactate is less effective than the desired stearyl lactyllactate. Col. 3, lines 56-57.
The reference recommends the use of 2.1 moles of lactic acid per one mole of stearyl alcohol (or cetyl alcohol), col. 1, lines 31-54, but suggests that the reaction of stearyl lactyllactate with an additional mole of lactic acid offered no appreciable advantages. Col. 3, lines 57-59. The Thompson patent also does not teach or suggest the use of a catalyst for the reaction of the alcohol with lactic acid. Because it is believed that alkyl lactyllactates are more efficient and can provide better performance and stability than alkyl lactates, it is desirable to have an improved process that can produce an alkyl lactyllactate product via a lactic acid route that contains a higher ratio of the lactyllactate component over the lactate component.
The alkyl lactyllactates and alkoxylated alkyl lactyllactates of the present technology can meet one or more of the above and other desirable attributes.